A Robust and Effective GNSS/INS Integration Optimizing Cost and Effort

Kurzfassung

Meeting all requirements for ying approaches in bad weather conditions is one of the most demanding and challenging aspects of present day airborne navigation. Stand-alone satellite navigation has not yet reached the point of being suciently robust and accurate in order to reach certication level. Therefore, in this work the performance of an integrated satellite/inertial navigation system (GNSS/INS) is investigated in order to cope with short term losses of GNSS signals. We consider a low-cost Micro Electronic Mechanical System (MEMS) INS which is constantly reinitialized with information coming solely from GNSS. It takes over navigational responsibility when a loss of signal occurs or other failures in the satellite navigation system are detected. For the GNSS to provide all information necessary to initialize an INS, a minimum of three antennas is needed to measure the aircraft's attitude along with its speed and position. Error models for positioning, speed and attitude estimation are used to create a model for initialization uncertainties. Together with error models for the accelerometers and gyros in the Inertial Measurement Unit (IMU), the behavior of the whole proposed architecture is determined via performance simulations. As a maximum allowable error 15.3 meters (which corresponds to the CAT III horizontal alert limit for GNSS approaches) are taken. Our simulations show that this limit is not exceeded for at least 14 seconds after the take-over of navigational responsibility by the INS.